Automatic defrost two-temperature refrigerator



y 15, 1962 A. G. JANOS ETAL 3,034,313

AUTOMATIC DEFROST TWO-TEMPERATURE REFRIGERATOR Filed Aug. 7, 1959 3Sheets-Sheet 1 I lllllllll INVENTORS I 3' AN 05 ALFRED c. DOUGLAS A.SOLLF-Y TR- 8 KENNETH A. ROBB|E T H E l R ATTORNEY May 15, 1962 A. G-JANOS ETAL AUTOMATIC DEFROST TWO-TEMPERATURE REFRIGERATOR Filed Aug. 7,1959 3 Sheets-Sheet 2 INVENTORS ALFRED e. J'ANOS,

DOUGLAS A. SOLLEY IR. & KENNETH A- ROBBIE T' H E l R ATTORNEY May 15,1962 A. e. JANOS ETAL 3,034,313

AUTOMATIC DEFROST TWO-TEMPERATURE REFRIGERATOR Filed Aug. 7, 1959 5Sheets-Sheet 3 INVENTOR-E ALFRED c1. u-Auos, DOUGLAS A. sou-Ev 1n.- 8,KENNETH A. ROBEnE BY WWW THEI R ATTORNEY United States Patent 3,034,313AUTOMATED DEFROST TWO-TEMPERATURE REFRIGERATOR Alfred G. Janos,Louisville, Douglas A. Solley, J12, Fern Creek, and Kenneth A. Robbie,Louisville, Ky., assignors to General Electric Company, a corporation ofNew York Filed Aug. 7, 1959, Ser. No. 832,221 1 Claim. (Cl. 62-155) Thepresent invention relates to household refrigerators and is moreparticularly concerned with a two-temperature refrigerator includingautomatically defrostable fresh food and freezer evaporators and to animproved freezer evaporator structure particularly adapted for automaticdefrosting operation.

Many of the present day refrigerators for household use include a freshfood storage compartment operating at temperatures above freezing and afreezer compartment operating at sub-freezing temperatures. Since theevaporator serving the fresh food compartment operates in an ambienttemperature that is substantially above freezing, an effective means fordefrosting the evaporator is to permit the evaporator to reach atemperature above freezing during each off cycle of the refrigeratingapparatus so that any frost which has collected thereon during theprevious on cycle will melt, the defrost water being disposed of outsideof the fresh food compartment.

Automatic defrosting of the freezer evaporator on the other handpresents a more difficult problem, one reason for this being that thedefrosting operation must be car ried out in such a manner that whilethe evaporator itself is warmed to a temperature above freezing, thecontents of the freezer compartment are maintained below freezing and atsafe frozen food storage temperatures during the defrost operation. Inaddition, it is essential that the entire freezer evaporator structurecome up to defrosting temperatures during the defrost cycle and that allof the condensate collected thereon be disposed of before the evaporatoris again refrigerated. Otherwise, ice in increasing amounts Willaccumulate on those portions of the freezer evaporator which are notcompletely defrosted and freed of defrost water. Such ice accumulationwill eventually interfere with the desired operation of the refrigeratoror at the very least constitute a source of annoyance to the user.

It is a general object of the present invention to provide atwo-temperature household refrigerator including automaticallydefrostable fresh food and freezer evaporators.

It is another object of the invention to provide a refrigeratorincluding an improved freezer evaporator which can be both quickly andeffectively defrosted and freed of condensate during the defrost cycle.

A further object of the invention is to provide in a freezer compartmentof a household refrigerator, a fan blown evaporator unit which isdesigned for good heat transfer between the evaporator cooling coil andthe air stream and for quick and complete frost and moisture removalduring a defrost cycle.

A still further object of the invention is to provide a simple andcompact defrostable evaporator structure from which condensate willreadily drain during a defrost cycle.

Further objects and advantages of the invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize the invention will be pointed out with particularity in theclaim annexed to and forming a part of this specification.

In carrying out the objects of the present invention, there is provideda combination refrigerator-freezer comprising an upper fresh foodcompartment, a lower freezer "ice compartment and separate evaporatorsfor maintaining the respective compartments at the desired operatingtemperatures. The defrostable evaporator unit for the freezercompartment includes a horizontally extending housing having front, rearand bottom walls, the front wall having an air inlet opening adjacentthe center portion thereof and air outlet openings adjacent each endthereof and the bottom wall being V-shaped to form a trough forreceiving defrost water. The evaporator coil disposed within the housingabove the bottom wall comprises parallel refrigerating and defrost tubeswhich are integrally connected throughout their lengths to form a smoothsurfaced structure from which moisture can readily flow during thedefrost operation. The coil includes a first section extending along therear wall of the housing and second and third sections along the frontwall, the second and third sections being spaced on opposite sides ofthe air inlet opening to permit the mounting of a motor driven fanwithin the housing opposite the opening in such a position that thecombined axial and radial air flow from the fan blades provides aturbulence within the housing which efiectively sweeps over all of thesurfaces of the coil for maximum heat exchange between the coil and theair. Disposed below the evaporator coil and connected to the outlet endof the re frigerant tube is a refrigerant accumulator that is nestedwithin the V-shaped bottom wall of the housing. The conduit forconducting hot refrigerant gas to the defrost tube component of theevaporator coil has one pass in heat exchange relationship with theV-shaped bottom wall of the housing so that both of these elements arewarmed to defrosting temperatures during the defrost cycle therebyfacilitating the flow of condensate from the housing during each defrostcycle.

For a better understanding of the invention, reference may be had to theaccompanying drawings in which:

FIG. 1 is a side elevational view, in section, of a refrigerator cabinetincorporating an embodiment of the present invention;

FIG. 2 is a front elevation, partly broken away, of the freezerevaporator unit of the present invention;

FIG. 3 is an elevation view of one end of the unit shown in FIG. 2 withthe end plate or wall removed;

FIG. 4 is a view similar to FIG. 3 of the opposite end of the evaporatorunit of FIG. 2;

. FIG. 5 is a sectional view taken along the line 55 of FIG. 2;

FIG. 6 is an enlarged sectional view of the accumulator forming part ofthe evaporator unit; and

FIG. 7 is a diagrammatic illustration of the refrigeration system andevaporator assembly of the present invention.

Referring now to the drawing, there is shown in FIG. 1 a householdrefrigerator of the two-temperature type comprising an outer shell 1 andinner shells or liners 2 and 3 spaced from the outer shell 1 and fromone another, the spaces being filled with suitable heat insulation 4.The upper shell 2 defines a fresh food storage compartment 5 which ismaintained at fresh food storage temperatures by means of a serpentineevaporator 6, while the lower liner 3 defines a freezer compartment 7maintained at subfreezing temperatures by an evaporator unit a. Therefrigerator also includes a machinery compartment 9 containing acompressor 10 and a condenser 11 for supplying condensed refrigerant tothe evaporators' 6 and 8.

The freezer evaporator unit 8 employed for maintaining the freezercompartment 7 at sub-freezing temperatures is preferably supported alongthe rear wall of the freezer compartment. This unit shown in greaterdetail in FIGS. 2 to 4 of the drawing comprises a substantially closedhousing including a front wall 12, end walls 13 and 14, a rear wall 15and a sloping V-shaped bottom wall 16. An evaporator coil generallyindicated by the numeral 18 is contained within the housing andcomprises a refrigerating tube 29 and a defrost tube 21 extendingparallel to the refrigerating tube in heat exchange relationship andpreferably in mechanical contact with the refrigerating tube. Thisstructure is preferably formed as a smooth surfaced double tubeextrusion so that the refrigerating tubing and the defrost tubing are inintimate mechanical contact throughout their lengths within the housing.By means of this double tube structure hot refrigerant gas can be passedthrough the defrost tube for periodic defrosting of the unit.Preferably, the hot gas flow is countercurrent to the refrigerant flowso that refrigerant is introduced into one end of coil and hot gas intothe other end.

The refrigerant inlet end or portion 23 of the evaporator coil which isconnected to the evaporator 6 extends through an aperture 24 provided inthe rear wall 15 of the housing and directly across the housing to forma horizontal pass 26. Most of the remaining portions of the evaporatorcoil are in the form of vertically elongated loops as illustrated inFIGS. 3 and 4 of the drawing, the loops extending from substantially thetopof the housing to the lower edges of the front and rear walls 12 and15 leaving a space below the evaporator coil 18 and generally'within theV-shaped bottom wall 16 for an accumulator 27 forming part of therefrigerating system.

With further reference to the evaporator coil, the coil comprises afirst section generally indicated by the numeral 29 extending along thelength of the housing adjacent the back Wall 15 and second and thirdsections 30 and 31 extending along the front wall 12 of the housing andrespectively positioned on opposite sides of an air inlet opening 33centrally located in the front wall 12. The refrigerant outlet end ofthe third section 31 is connected to one end of the accumulator 27.

The use of a double tube extrusion or an equivalentstructure Whichpresents a substantially continuous and smooth tube surface and theforming of the double tube extrusion into a plurality of verticallyelongated loops having relatively sharp return bends atthe tops andhottoms thereof provides a coil from which frost can be quickly removedby passing hot refrigerant gas through the defrost tubing 21. Uponmelting of the frost, the

condensate readily flows downwardly along the vertical surfaces of thevarious loops and drips oif the sharp return bends or bottom portionsthereof into the trough formed by the V-shaped bottom wall 16 from whichit is discharged into a drain 60. An important feature of the evaporatorcoil is its freedom from fins or other struc- .coil 18 by means of a fan37 which is positioned as indicated in FIG. 1 within the housing inapproximately the same plane as the evaporator coil sections 30 and 51or in other words with the fan blades 38 in substantial alignment withthese coil sections. A motor 39 for driving the fan 37 is also locatedwithin the housing and if V necessary some of the loops comprising thefirst evaporator coil section 29 may be spaced apart opposite the airinlet opening 33 to provide room for the motor 39. Air

drawn into the housing 'by the fan through the air inlet 33 passes overthe evaporator coil portions on each side of the air inlet 33 and isdischarged back into the compartment 7 through a plurality of louvers orair outlets 41 provided in the housing and adjacent the opposite endsthereof. By placing the fan blades 38 within the housing rather than inthe plane of the front wall 12 or outside of the housing an increasedturbulent air flow through the housing is obtained which assures amaximum heat exchange contact of the air stream and the various loopscomprising the evaporator coil 18. The radial air flow from the tips ofthe fan blades 38 is directed particularly over the front sections 30and 31 of the evaporator coil while axial air flow from the fan bladescontacts the rear wall 15 of the housing and then spreads outwardlytowards the ends 13 and 14 of the housing to sweep the rear or firstcoils section 29. The mixing of these two air streams within the housingprovides a turbulent air flow assuring freedom from any dead air spaceswithin the coil structure.

During normal or refrigerating operation of the refrigcrating systemschematically shown in FIG. 7 compressed refrigerant from the compressor10 is condensed in the condenser 11 from which it flows through acapillary tube 43 into evaporator 6 where at a lower pressure a portionof the liquid refrigerant evaporates to cool the contents of the freshfood compartment 5. In the referigerating system employed in thepractice of the present invention the fresh food evaporator 6 and thefreezer evapora tor tubing 20 are designed to operate at the samepressures and at below freezing temperatures when the compressor isoperating. They are therefore connected by a non-restricting tube 44.Refrigerant liquid and gas flows from the evaporator 6 into tube 20Where some or all of the remaining liquid evaporates. Any liquidrefrigerant not evaporated in the refrigerant tubing 20 forming part ofthe evaporator unit 8 collects in the accumulator 27 from which thegaseous refrigerant is Withdrawn through the suction line 45 by thecompressor 10.

For the purpose of defrosting the freezer evaporator structure 8, hotrefrigerant gas from the compressor 10 is periodically passed throughthe defrost tubing 21 employing a defrost arrangement and circuit morefully described and claimed in the copending application of Clyde J.Nonomaque filed November 25, 1957 and assigned to the same assignee asthe present invention. The inlet end 49 of the conduit 51 forming partof defrost circuit is connected to the refrigerating circuit between thecompressor and the condenser 11 and a normally closed valve 50 isprovided for the purpose of controlling the flow of refrigerant throughthe defrost circuit. When this valve is opened hot compressedrefrigerant flows through the conduit 51 which contacts the drain 60 andalso includes a pass 52 for Warming the V-shaped bottom wall 16 of thehousing and a pass 53 extending along the exterior of the accumulator 27for heating the accumulator. The pass 53 is connected to the defrosttubing 21 which, as has previously been indicated, follows or parallelsthe refrigerant tube 20 throughout the evaporator coil 1-8 and passesout through the opening 24 in engagement with the inlet end of therefi'igerant tube 20. In order to assure complete defrosting of theentire refrigerant tubing 20 within the freezer compartment, the defrosttub ing 21 continues upwardly in contact with the refrigerant tubingthrough the insulated space between the outer shell 1 and the liners toa point between the freezer evaporator unit 8 and the evaporator 6 whereit connects. with a capillary tube 56 through which the refrigerant is.returned to the suction line 45 and the compressor 10.v For a moredetailed description of the operation of this. defrost circuit referenceis made to the above-mentioned Nonomaque application.

As the hot gas passing through the defrost line or tube 21 warms thebottom Wall 16 of the housing, the accumulator 27 and the evaporatorcoil 18 to temperatures above freezing, any frost collected on thesesurfaces or on any adjacent Walls of the housing is quickly melted. Thedefrost water flowing down the walls of the housing or dropping from thebottom bends of the vertical loops forming the evaporator coil iscollected in the V-shaped bottom wall 16 and is discharged into thedrain 60 which is provided below the lower end of the sloping bottomwall 16, and which is also warmed to above-freezing temperatures by thehot gas flowing through conduit 51.

The drain disposes of the defrost water outside the freezer compartmentand preferably directs it into the machinery compartment 9 where areceptacle (not shown) may be provided for receiving the condensate andevaporating it by means of the heat from the compressor and condenser.

For the purpose of obtaining good heat transfer between the accumulator27 and-the loop 53 of the defrost tubing employed to warm theaccumulator during a defrost cycle, the accumulator is'preferably formedin the shape of an elongated tube having flanges 60' extending outwardlyfrom the walls thereof, the flanges being shaped to accommodate thedefrost tubing 53. As shown more clearly in FIG. '6 these flanges areemployed to clamp the defrost tubing into tight heat transfer engagementwith the accumulator 27 thus assuring good heating contact between theaccumulator and the defrost gas and also serving as a means forsupporting the defrost tubing 53 in this area.

The electrical control system for controlling the refrigeratingoperation of the refrigerating system and for periodically defrostingthe evaporator unit by means of hot gas from the compressor is alsoillustrated in FIG. 7 of the drawing. For normal refrigerating control,the circuit comprises a pair of supply lines or conductors 64 and 65 forenergizing the compressor 10 through a temperature-operated switch 66. Atemperature sensing device 67 positioned in contact with the outlet endof the evaporator 6 within the fresh food storage compartment 5 operatesthe switch 66 so that during normal operation of the system, thecompressor is energized whenever that evaporator 6 reaches apredetermined above-freezing temperature of, for example, F. and isopened when the temperature reaches a low temperature of, for example, 0F. Since there is substantially no restriction between the evaporator 6and the refrigerant tubing 18 forming part of the evaporator unit 8,both of these units reach almost the same minimum temperature duringeach on or refrigerating cycle. However, as the evaporator 6 is of asmaller mass and is in a warmer environment that evaporator structure 8,its temperature will rise to an above freezing temperature during eachoff cycle while the freezer evaporator structure 8 experiences a muchslower temperature rise and will operate continuously at below freezingtemperatures.

For the purpose of automatically initiating periodic defrost operationfor the freezer evaporator structure 8, there is employed a defrostcontrol circuit which periodically energizes and opens the solenoidvalve to permit flow of gaseous refrigerant from the high pressure sideof the system, that is from the compressor, through the defrost circuit.In the illustrated modification of the invention, periodic defrosting iscontrolled by a timer 68 connected across the supply lines 6465 whichtimer operates a switch 69 that controls the operation of the solenoidvalve 50 and the fan motor 39. The switch 69 includes normally closedcontacts 70 by means of which the fan motor 39 is normally energized foroperation of the fan 37 whenever the compressor is energized by closingof switch 66. At predetermined intervals, the timer motor 68 operatesswitch 69 to open normally closed contacts 70 in the fan circuit andclose a contact 71 to energize and open the solenoid valve 50. Bystopping the fan 37 during defrost, air circulation between theevaporator unit and the compartment 7 is kept at a minimum. Since theoperation of the timer is independent of the refrigerating controlswitch 66, the energization of the solenoid 50 may take place duringnormal refrigerating cycle when the compressor is operating or during anoff cycle. If the compressor is operating, hot refrigerant from thecompressor will immediately be directed through the defrost circuit. Ifthe compressor is not operating, the defrost flow of refrigerant is theninitiated at the beginning of the next on cycle when the switch 66 againenergizes the compressor in response to a predetermined rise in thetemperature of the fresh food evaporator 6.

For the purpose of terminating the defrost cycle after a completedefrosting of the evaporator structure 8 there is provided a sensingbulb 74 forming part of abellows arrangement 75 adapted to trip theswitch 69 and return it to its normal refrigerating position in whichthe fan motor 39 is energized and the solenoid valve '50 is closed. Thesensing bulb 74 is preferably positioned in contact with the horizontalpass 26 of the evaporator coil 18 adjacent the outlet end of the defrosttubing 21 as this will normally be thelast portion of the evaporatorstructure to reach defrosting temperatures.

During the defrost operation, hot gas flowing through the conduit 51first warms the drain 60 so that defrost water collecting in the trough16 can flow through the drain and outof the freezer compartment 7. Thepasses 52 and 53 are the next portions of the defrost circuit to becomewarm and respectively heat the bottom or trough portion 16 of thehousing and the accumulator 27 so that these portions of the evaporatorstructure are quickly brought up to defrosting temperatures and theaccumulator emptied of liquid refrigerant to assure complete defrostingthereof. Thereafter the coil 18 is warmed to complete the defrostoperation.

By extending a portion of the defrost line or tube 21 upwardly to theconduit 44 connecting the upper and lower evaporators sufiicient heatingof refrigerant line 20 in this area is obtained to assure completemelting of the frost on the portions of the refrigerant tube 2t withinthe housing.

In the light of the foregoing description, it will be seen that thepresent invention provides an improved twotemperature refrigerator inwhich both the fresh food and freezer evaporators are automaticallydefrosted. The structure of the evaporator unit 3 employed formaintaining the freezer compartment 7 at sub-freezing temperatures issuch that during each defrost operation all of the defrost water willquickly drain from the frosted surfaces due both to the design of theevaporator coil 18 which assures quick drainage of moisture from thecoil surfaces and also by the arrangement of portions of the defrostcircuit in contact with the drain, the bottom wall 16 of the housing andthe accumulator. By arranging the fan 37 within the housing and therebyproviding a turbulent flow of air through the housing, the required heattransfer between the air circulated through the housing and theevaporator coil 18 is obtained without the use of fins or other heattransfer surfaces normally employed in connection with such structures.

While there has been shown and described a particular embodiment of thepresent invention, it is to be understood that the invention is notlimited to this embodiment and it is intended by the appended claim tocover all modifications within the true spirit and scope of theinvention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

A combination refrigerator-freezer comprising an upper fresh foodcompartment and a lower freezer compartment, an evaporator in said uppercompartment and a low temperature defrostable evaporator unit in saidlower compartment, said unit comprising a horizontal housing supportedalong one wall of said freezer compartment and including a front wallhaving a centrally positioned opening therein and air outlets adjacentthe ends thereof, and a V-shaped bottom wall, a double-tube evaporatorcoil disposed in said housing in the form of a plurality of verticallyelongated loops arranged between said central opening and the oppositeends of said housing, said coil comprising a refrigerating tube and adefrost tube in parallel heat exchange relation with said refrigeratingtube, an accumulator chamber supported on said V-shaped bottom wall ofsaid housing, a compressor, a condenser, a capillary flow restrictor, asuction line, conduit means connecting said compressor, condenser, flowrestrictor, high temperature evaporator, refrigerating tube, andaccumulator in series flow refrigerating circuit end'of said defrosttube and a second conduit including a flow restricting means connectingthe outlet end of said defrost tube to said suction line, said firstconduit including a first pass in heating engagement with said V-shapedbottom Wall and a second pass in heating engagement with saidaccumulator, a fan disposed in said opening for circulating air fromsaid freezer compartment through said housing and back to saidcompartment, and electrical control means for controlling the operationof said compressor, valve and fan'in'cluding compressor control meansfor energizing said compressor only after said high temperatureevaporator has reached a temperature above freezing and tie-energizingsaid compressor when said high temperature evaporator has reached atemperature below freezing and defrost control means including a timerfor periodically opening said valve and de-energizing said fan fordefrosting said low temperature evap- References Cited in the file ofthis patent UNITED STATES PATENTS 1,827,410 Warren Oct.13, 19312,158,090 Smith May 16, 1939 2,366,635 McCloy Jan. 2, 1945 2,463,835Warren Mar. 8, 1949 2,528,720 Binder Nov. 7, 1950 2,584,442 Frie Feb. 5,1952 2,637,983 Malkofi May 12, 1953 2,688,850 White Sept. 14, 19542,794,325 Shearer June 4, 1957 2,801,525 Bixler Aug. 6, 1957 2,801,528Parcaro Aug. 6, 1957 2,882,696 Herrmann Apr. 21, 1959 2,894,379 Saunders"July 14, 1959 2,895,307 Nonomaque July 21, 1959 2,909,907 Swanson Oct.27, 1959 2,940,279 Schumacher June 14, 1960 2,987,854 Gould June 27,1961

